BENGALURU: With the successful launch of IRNSS-1I, the eighth Indian Regional Navigation Satellite System (IRNSS), by the Indian Space Research Organisation (ISRO) early Thursday morning, space scientists are looking at positioning the satellite in space to join the other seven already in space to deliver indigenous navigation services to Indian land-based users.
When the “Navigation with Indian Constellation (NavIC)” system (the other name for IRNSS) is up and operational later this year or early 2019, a global positioning system (GPS) unit attached to your vehicle, or through an application on your mobile phone, will be able to direct you to your destination accurately.
NavIC will ultimately also help users find precise locations providing specific goods and services (including restaurants, theatres, hospitals, schools, hotels, etc) when these register with the system for users to find them easily using the satellite service.
NavIC system covers the entire Indian mainland and 1,500 km beyond the country’s borders, and Prime Minister Narendra Modi is already on record saying friendly neighbouring countries could also be provided the service when the system is operational.
According to ISRO, NavIC system presently comprises the entire constellation of eight satellites — IRNSS-1A, 1B, 1C, 1D, 1E, 1F, and 1G which are already in their orbital homes in space over India — with IRNSS-1I joining the other seven.
Although only seven satellites were initially planned for NavIC constellation, IRNSS-1I has been sent up to compensate for the malfunctioning of the atomic clock on board IRNSS-1A and the failed mission of IRNSS-1H (which was initially planned to compensate IRNSS-1A’s malfunctioning atomic clock) on August 31, 2017. With the redundant atomic clock of IRNSS-1A, there would be only six satellites with functioning atomic clocks if IRNSS-1I wasn’t launched on Thursday. IRNSS-1I is effectively the ninth satellite sent up for the NavIC initiative.
The 1,425-kg IRNSS-1I was successfully launched at 4.04 am on Thursday on board PSLV-C41 from ISRO’s First Launch Pad at Satish Dhawan Space Centre SHAR, Sriharikota. It was the 43rd flight of ISRO’s workhorse launcher Polar Satellite Launch Vehicle.
After a flight lasting 19 minutes, the vehicle achieved a Sub Geosynchronous Transfer Orbit with a perigee (nearest point to earth) of 281.5 km and an apogee (farthest point to earth) of 20,730 km inclined at an angle of 19.2 degree to the equator following which IRNSS-1I separated from PSLV.
After separation, the solar panels of IRNSS-1I were deployed automatically. ISRO’s Master Control Facility (MCF) at Hassan in Karnataka took over the control of the satellite.
In the coming days, orbit-raising manoeuvres will be performed from MCF to position the satellite at 55 deg east longitude in the planned Geosynchronous Orbit with an inclination of 29 deg to the equator. The first orbit raising operation of IRNSS-1I was planned to be carried out at 4.15 am on Friday.
Like its other IRNSS predecessors, IRNSS-1I also carries two types of payloads – navigation payload and ranging payload. The navigation payload of IRNSS-1I transmits signals for the determination of position, velocity and time. This payload is operating in L5-band and S-band. Rubidium atomic clocks are part of the navigation payload of the satellite.
HOW NavIC WORKS
For accurate positioning of the user on the land, his/her receiver should receive signals from a minimum of four satellites. But NavIC has seven.
More the number of satellites in this system, better is the accuracy of positioning.
The location of the user and the destination and the distance and directions are calculated by the precise time taken for the signals (at speed of light) from the various satellites in the constellation.
The destination is entered by the user (for example a driver who is trying to find his destination), which is picked up by navigation payload on satellite and relayed back to the user for location of destination.
The precise location and distance between user and destination and the directions to get there, are determined by highly accurate measurement of the radio signal’s travel time from the satellite to the users’ receivers.
This arrives on the users’ screens to help them navigate and find the destination.